BARNES — NORTH AMERICAN MOSSES. 249 



Plants small (usually less than 5 cm.). 

 PerichiBtial leaves plicate. 



Inner perichaetial leaves costate. 

 Alar cells not distinct i . . . . ' . H. fertile, 391. 

 Alar cells large, hyaline . . . H. Wagliomei, 565. 



Inner perichaetial leaves ecostate . . . H. hamiilosiim, 391. 

 Perichaetial leaves not plicate. 

 Alar cells not enlarged . . . . H. subimpouens, 393. 

 Alar cells quadrate or vesicular, enlarged. 

 Leaves narrowly acuminate, faintly bicostate H. depressulum, 391. 

 Leaves long subulate, ecostate . . . H. circinale, 392. 



2. Plants irregularly branched. 



[H, callicJivount may be sought here] 



* Leaves quite entire. 



Alar cells not different H. pseudoarcticum, 5S4. 



Alar cells enlarged, oblong rectangular. 



Teeth hyaline margined, cilia appendiculate H. arcuatiforme, 576. 



Teeth not hyaline margined, cilia nodose . . H. prateiise,- 397. 

 Alar cells quadrate. 



Plants erect, fastigiately branched . . . H. Bambergeri, 397. 



Plants prostrate, irregularly pinnate . . H. incurvatuin, 600. 



* * Leaves serrulate or denticulate above. 



[H. pseudo-arcticuni and H. iticurvatutn may be sought here.] 



Perichaetial leaves costate, and plicate or sulcate. 



Costa geminate, reaching middle . . . . H. reptile, 390. 

 Costa geminate, short. 



Middle leaf cells long (1 : 12-15) . . H. cupressiforme,^ 394. 

 Middle leaf cells shorter (1 : 6-8) . . . H. Vauclieri,* 570. 



Costa single, or wanting. 

 Inner perichaetial leaves long subulate (1 : 12) . H. Moseri, 559. 



Inner perichfetial leaves lanceolate (1:5) . H. fastig-iatum, 564. 



1 "Blattflugelzellen sehr gross, aufgeblasen, wasserhell bis gold gelb," sec. Milde, Bry. 

 Siles. 359. Not according to Bryol. Eur. pi. 591, from which this character is taken. 



^ See Appendix, no. 578. 



' See Appendix, no. 569. 



* The character of the perichaetial leaves is unknown to me, but since the species is 

 so closely related to H. cupressi/orme, it is placed in this position. 



